8-Bit Software

The BBC and Master Computer Public Domain Library

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Alastair Seggie's Starturn Lathe Nightmare

By Chris Richardson


Alastair Seggie first contacted me wanting ot copy an Eprom for his CNC lathe, controlled by a Master. All seemed fairly simple to me to start with, a simple software and ROM copy. I had done this thing many times before for various people (with the blessing of the owners of the copyright I hasten to add).

The ROM turned out to be a nightmare, as I write this, the problem is not solved. I am hoping that someone that knows something about this might be able to 'chip' in and help (sorry about that!)

At first I thought it was one of those large Eproms, sat on a carrier board, the small chip on the carrier board switching banks for the computer. Then we discovered that the chip was only an 8k one so it became horribly obvious that the carrier board and small chip were protection for the software

Here is a message that Alastair put on the 8BS message board:

I am trying to get a CNC lathe working. A Denford Starturn 8 to be precise. I now have everything: the lathe, a BBC Master and all ancillaries, the leads and the software. Now all I need is the EPROM which acts as a dongle type device. Now this EPROM is a normal 28 pin device that goes in to a socket on the top of a small PCB. It has a second 20 pin chip under it on the PCB then it has turned Pins which go into the ROM socket. How does one copy such a device? Does anyone have one? It can be identified by "SYNTEL 84" on the underneath of the PCB.

Here are some photographs of the chip:
1. In situ - ROM in the BBC
2. Top with EPROM - this gives a view from the top of the carrier clearly showing the Toshiba EPROM.
3. Top WO EPROM - This shows the carrier with the EPROM removed so the 20-pin device is shown.
4. Side - Shows a side view of the carrier
5. Bottom shows the pin side of the PCB as well as the carrier identification markings.
6. Starturn ROM - is a schematic (which is my first so no sniggering) this was based on the enclosed data sheet I could not find the one for the Toshiba EPROM.
7. Main board shows a similar 20-pin device on the main board (inside the lathe) could this are an encoder decoder situation?

A PDF datasheet

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